Getting 0% and 100% active PWM signal with 555

[SAV]

I am working on a very low cost design that includes a PWM for a DC Motor control. I choose a 555 working in monostable configuration for that work but i can't get 0% and 100% active signal into the cycle. It's posible to get this?

 

[flatulent]

555 pwm

It is not very likely. You can take the capacitor voltage and have your own comparator measuring it compared to the DC level you supply to it. That way you will get your full range.

 

[IanP]

cpe mma co uk 555 pwm

The best you can do using 555 will be between 5% and 95% (examples: http://www.cpemma.co.uk/pwm.html#nomad ). Even using ICs such as LM3524 or similar you will be able to achieve 0% but the Max ration will be around 50-60%.
To cover full range you will have to use a microcontroller with,s ay, 8-bit PWM. This will give you 256 different ratios from 0% to 100%..

 

[ericjohnson]

pwm with 555

I think Sandra & Smith book is a good reference.
-EJ

 

[Ante]

pwm using 555

You can have 0.5 to 99.5% it you like with a 555.

 

[nvd]

pwm con 555

Another possibility is to produce a triangular wave. Input it at the + input of the op-amp. Use a potential divider at the - input of the op-amp. By varying the voltage at - input, you can have square pulses of any width.

 

[fsmyth]

cpe mma co uk pwm

There are a few examples, with associated calculations, at:
**broken link removed**
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